The present invention relates generally to catheters for monitoring body temperature and more particularly to a device for use in hyperthermia systems during patient treatment.
Both whole body hyperthermia and local hyperthermia are procedures known in the art. Whole body hyperthermia is a disease treatment technique or therapy that has been used to treat a number of diseases. In operation, blood is removed from the body and heated externally to a target temperature and then returned to the body. Various treatment protocols have been proposed and several studies have been directed to assessing the efficacy of the therapy for several disease indications. Suitable structures for carrying out whole body hyperthermia are known from U.S. Pat. No. 5,391,192 to Sites et al., incorporated herein by reference. A microprocessor-based hyperthermia is known from the Optichem SLH 100 system. Experimentation has also been performed with conventional perfusion devices. Although the efficacy of the therapy is now established, there is a continuing need to improve the devices used to carry out this procedure. For example, efficacy is improved with accurate knowledge and control of body temperature.
The present invention improves the ability to monitor and control the blood and body temperature. An improved temperature monitoring device is especially well suited to whole body hyperthermia, but may be useful in other patient care settings as well.
A catheter is described in the context of a whole body hyperthermia system. However, this use is illustrative and should not be taken as limiting the invention. In use, the catheter is suspended in the bladder of the patient. A cuff on the catheter inflates after the catheter is inserted in the bladder to assist in positioning and securing the catheter. The catheter has a temperature sensor proximal of the inflatable cuff to measure body temperature at the urinary sphincter muscle. The sensor is located relative to the cuff a distance known to generally correspond to the typical distance between the bladder and the sphincter muscle in humans. This distance is known to be approximately the same amongst humans regardless of size.
In an alternative embodiment, a second temperature sensor is placed distal of the inflatable cuff and thus monitors the temperature of the urine pool in the bladder. Each of the measurements from the first and second temperature sensors has a different time constant depending on the volume of urine in the bladder, and the level of perfusion in the sphincter. Data from these two sensors, the differences between the readings, and the time-dependent variation of these two sensors can contribute to the overall efficacy of the device.